test(agentcompat): add process supervision harness

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

integration/agentcompat/internal/process/supervisor_agentcompat.go

@@ -0,0 +1,7 @@
+//go:build linux && agentcompat
+
+package process
+
+func (supervisor *Supervisor) CleanupDoneForTest() <-chan struct{} {
+	return supervisor.cleanupDone
+}